Seeking Greater Speed from Wind

In the 19th century, the 440-foot, 11,000-ton German built Preussen could achieve a sailing speed of 17 knots from 59,000-square feet of sail. However, the development of coal-fired steam propulsion and steady improvements to steam engines resulted in such ships sailing sustained in excess of 20 knots. 

Despite the demise of wind-driven propulsion from commercial ship transport, boat enthusiasts have continually sought to increase the sailing speed of wind-driven sailing vessels. Within the past five years, wind powered sailing vessels have achieved a speed of over 50 knots from a crosswind of 28 knots. The design of the vessel included hydrofoils attached to a transversely mounted aeronautical style of wing. When sailing at speed, very little of the vessel was actually in contact with the sea. 

While sailing enthusiasts seek to develop a faster wind-driven vessel, other related developments are occurring in the world of maritime technology that could, at a later time, be incorporated into the design of fast moving, wind-powered vessels. One area of innovation involves refinements to airborne kite-sail technology while other enthusiasts are developing and refining wing-in-ground effect vessels for future market application.

Kite Sails

The technology of airborne kite sails are being applied to commercial ships to assist propulsion of a container ship and also to propel a comparatively small passenger vessel used in the tourist trade. Sailboard enthusiasts make widespread use of kite sails as their source of propulsion. 

Development of kite-sail technology is the result of the discovery that winds at higher altitude blow at higher velocity. There is potential to further develop kite-sail propulsion and adapt the technology to large-scale, ocean capable sailing vessels that can undertake extended voyages while riding on hydrofoils attached to wing-like structures. 

The vessels may sail parallel to the direction of prevailing trade winds with kites at elevations of about 3,000-metres, the flight altitude allocated to propeller-driven commuter aircraft. A kite-sail flying at such altitude could theoretically pull a hydrofoil vessel travelling in the same direction as the wind, at near record breaking speeds over greatly extended distances. 

Airborne kite-sails that are secured to the bow of cargo ships fly at relatively low elevation while reduce fuel consumption by between 20 and 40 percent, representing 5,000 to 10,000-horsepower for ships that sail at an average speed of 20 knots.

Wing-in-Ground Effect

Several companies located across the Asia-Pacific region in China, South Korea, Australia, Singapore and Malaysia have been actively working on developing sea-going, wing-in-ground effect technology for civilian application. These vessels use a wing profile based on that of large seabirds that can glide close to the water surface for greatly extended distances, while expending minimal energy. High-speed yachts with vessel-mounted sails incorporate wing structures into their hulls design to assist the hydrofoils. 

A future competition could involve wind powered vessels sailing across ocean and parallel to the direction of trade winds. Such a competition would invite consideration of airborne kite-sails to gain access to high-speed winds that blow at high elevation. Towing cables made from lightweight, high-strength super-fiber could connect between vessel and airborne kite-sail. 

The combination of wind speed near ocean surface being a small fraction of high-altitude wind speed invites vessel designers to incorporate aspects and features of wing-in-ground (WIG) effect technology into the design of wind-powered trans-oceanic vessels. Vessels originally design for competition could form the basis of the design of future wind-powered, trans-oceanic vessels intended to carry tourists of even fast freight.

Twin-Hull Parallel Masts

California based wind power developer Douglas Selsam built the multi-rotor super turbine that places multiple turbines on the same propeller-shaft that is mounted at an angle to the wind. By offsetting each successive rotor, prevailing wind interacts will all or part of each rotor to increase power delivery. The precedent may be applied to multi-hull boats with each hull carrying one or more masts that are set further apart than masts on a mono-hull vessel and also staggered transversely. Such layout assures fast wind speed between the leading masts and fast wind speed on the trailing masts.

The Selsam concept can also be applied to kite-sails. Kite builders long ago learned how to fly kite trains that involve successive kites at progressively higher elevation on the same control lines. Specifically designed kite trains could pull future wind-assisted or wind powered vessels, including vessels intended to sail at elevated speed in a parallel direction to trade winds. 

New developments in frameless, air-cell kite technology can provide kites of high tensile strength that can be retracted and folded to occupy small and compact space. Such kites could be adapted to multi-hull vessels and fly in a V-formation.

Conclusion

While steam powered and diesel powered ships replaced wind-powered commercial sailing, ongoing developments in kite technology produced kite-sails that tow surfboards. Gigantic versions of the same kite-sail design have proven capable of helping to pull a modern commercial ship. Future development of the technology would likely involve trains of kite-sails pulling vessels that sail parallel to the trade winds. New innovations in wind-powered boats have resulted in the appearance of a vessel that has sailed at three times the speed of the Preussen. Other concepts in wind propulsion and sailing technology are already proven in other applications.

Perhaps the next step in wind powered sailing would be to combine trains of kite-sails in a vessel that also combines hydrofoil technology with wing-in-ground effect technology. There would be potential for such a vessel to carry passenger on trans-oceanic voyages. Trains of kite sails that fly at successively higher elevation could stow in compact space when retracted and when deployed, pull commercial ships to further reduce fuel consumption on trans-oceanic voyages compared to a single kite-sail. 

New ideas in wind propulsion and wind-assisted propulsion could still find application in modern maritime transportation.